Future tactical data links, electronic intelligence collection systems and high resolution radar receivers demand high performance, large time-bandwidth product devices for signal processing. Fiber and integrated optics technologies promise to provide versatile and effective signal processing techniques with bandwidths and time-bandwidth products exceeding those of any other technology currently envisioned. Other potential benefits include reduced size, weight, cost and complexity and reduced sensitivity to electromagnetic interference, electromagnetic pulse and nuclear radiation.
It is known to construct a segment of optical fiber which is resonant to the optical or carrier frequency by placing highly reflecting mirrors on both ends of the fiber and injecting light of appropriate characteristics into the fiber. A fiber segment so configured may be referred to as a resonant cavity with respect to the carrier frequency. This has been described as being useful for determination of coupling coefficients to enable one to specify and predict the light transmission characteristics of a particular fiber. This assumes the use of a multimode fiber segment where the coupling coefficients between at least two light propagating modes which are simultaneously at resonance within the fiber segment are measured.
It has not previously been suggested that a multimode optical fiber functioning as a resonant cavity may be employed, with its attendant advantages relating to cost, size, weight and reduced susceptibility to external interference, as an RF bandpass filter.